1. Field of the Invention
This invention relates in general to a paper-feeding apparatus for use on a printing machine, such as a computer printer, a copy machine, a fax machine, and the like, to feed paper sheets through the printing process.
2. Description of Related Art
A conventional paper-feeding apparatus for use on an inkjet printer is disclosed in U.S. Pat. No. 5,419,543 to Nakamura et al., which is illustrated in FIGS. 8-9.
As shown in FIG. 8, the paper-feeding apparatus of U.S. Pat. No. 5,419,543 includes a printer body 1, a paper guiding path 90, a paper setting mechanism 10, a paper feeding mechanism 20, a printing head 3, a paper delivery mechanism 91, and a paper receiving portion 7. Moreover, on the printer body 1, there is provided a drive gear mechanism 50 which uses a motor 51 to drive both the paper setting mechanism 10 and the paper feed mechanism 20. Further, the rotational direction of the motor 51 is controlled by a drive control means 70.
Referring further to FIG. 9, the drive gear mechanism 50 includes a motor 51, a pinion gear 52 axially mounted on the shaft of the motor 51, a first gear portion (including a cam gear 53 and an intermediate gear 54) coupled to a cam member 14 on the paper setting mechanism 10, a second gear portion (including a paper feeding gear 55) meshed to the feed roller 21 on the paper feeding mechanism 20, and a selective power transmission portion 61. Further, the selective power transmission portion 61 includes a sun gear (a power transmission mechanism) 62 meshed to the pinion gear 52; a swing mechanism (a selecting mechanism) 63 axially coupled to the shaft 62a of the sun gear 62 and rotatable in the same direction as the sun gear 62; and a planet gear 64 provided on the swing mechanism 63 and meshed to the sun gear 62.
When the motor 51 drives the pinion gear 52 to rotate in the clockwise direction, the sun gear 62 in the selective power transmission portion 61 will be forced to rotate in the counterclockwise direction. This causes the swing mechanism 63 to swing in the counterclockwise direction and the planet gear 64 to be meshed to the intermediate gear 54 in the first gear portion. As a result, the power from the motor 51 is transmitted to the cam member 14, causing the cam member 14 to rotate in the clockwise direction as indicated by the arrow in FIG. 9. At this time, if the cam member 14 is disengaged from the cam-contracted surface 11c on the bottom of the paper tray 11, the spring 13 will press upwards against the paper tray 11, causing the paper tray 11 to come into abutment on the feed roller 21, thereby allowing the sheets in the paper tray 11 to be fed in by the feed roller 21. Otherwise, if the cam member 14 is in contact with the cam-contacted surface 11c, the cam member 14 will press downwards against the paper tray 11, thereby compressing the spring 13 and causing the paper tray 11 to withdraw from the feed roller 21.
On the other hand, when the motor 51 drives the pinion gear 52 to rotate in the counterclockwise direction (as indicated by the arrow in FIG. 9), it will drive the sun gear 62 to rotate also in the counterclockwise direction, causing the swing mechanism 63 to swing in the clockwise direction. This then causes the planet gear 64 to be meshed to the paper feeding gear 55 in the second gear portion. As a result, the power from the motor 51 is transmitted to the feed roller 21, causing the feed roller 21 to rotate in the clockwise direction. At this time, if the paper tray 11 is in abutment on the feed roller 21, the topmost sheet in the paper tray 11 will be drawn out by the feed roller 21 to be fed into the printing process.
The foregoing paper-feeding apparatus is specifically designed to use just one driving motor to drive the paper setting mechanism and paper feeding mechanism of a printing means. In contrast in more conventional apparatuses two driving motor are used. The use of two driving motors increases the structural complexity of the apparatus, and thus the manufacturing cost. Although the foregoing paper-feeding apparatus can sole this problem, it nonetheless has some other drawbacks. The patented apparatus utilizes two sets of transmission mechanisms, i.e., the drive gear mechanism 50 and the selective power transmission portion 61, which still increases the structural complexity of the apparatus. The high structural complexity increases the manufacturing cost while the resultant apparatus bulky in size. Furthermore, the use of a single-directional clutching mechanism in place of the swing mechanism 63 also increases the structural complexity and thus the manufacturing cost of the apparatus.